Method, computer program and device for measuring the injection quantity of injection nozzles,especially for motor vehicles

ABSTRACT

In a method for measuring the injection quantity of injection systems ( 32, 33 ), in particular for motor vehicles and in particular in production testing, an injection system ( 32, 33 ) injects a testing fluid into a measuring chamber ( 45 ). A detection device ( 68 ) detects a movement of a piston ( 40 ), which at least partially defines the measuring chamber ( 45 ). This detection device ( 68 ) generates a corresponding measurement signal (sm). In order to increase the precision of the calculation of the injected testing fluid mass, the invention proposes that the pressure (p) of the testing fluid in the measuring chamber ( 45 ) be detected and that the measurement signal (sm) be processed ( 80 ) taking into account the detected pressure (p).

PRIOR ART

[0001] The current invention relates first to a method for measuring theinjection quantity of injection systems, in particular for motorvehicles and in particular in production testing, in which a testingfluid is injected into a measuring chamber by an injection system andthe injection-induced movement of a piston, which at least partiallydefines the measuring chamber, is detected by a detection device, whichtransmits a measurement signal.

[0002] A method of this kind is known from the market. The method isapplied by using a device, which is referred to as an injected fuelquantity indicator. This component is comprised of a housing in which apiston is guided. The inner chamber of the housing and the piston definea measuring chamber. This measuring chamber has an opening against whichan injection system, for example an injector with an injection nozzle,can be placed in a pressure-tight manner. When the injection systeminjects fuel into the measuring chamber, a fluid contained in themeasuring chamber is displaced. This causes the piston to move, which isdetected by a distance sensor. The volume change of the measuringchamber and of the fluid contained therein and therefore the quantity offuel injected can be calculated from the distance traveled by thepiston.

[0003] In the known injected fuel quantity indicator, a device comprisedof a measuring plunger and an inductive distance measuring system isused to measure the movement of the piston. The measuring plunger isembodied as a probe or is connected to the piston. When the pistonmoves, this also causes the measuring plunger to move and finally, themovement of the measuring plunger is detected and a corresponding signalis sent to an evaluation unit.

[0004] The known method already operates with a very high degree ofprecision with regard to the detected movement of the measuring plunger.However, the mass of the injected testing fluid calculated from thismovement and the volume of injected fuel likewise calculated from itfall somewhat below the path measurement in terms of the precision. Thisproblem is more intense the smaller the movement of the piston is, i.e.the smaller the injected testing fluid quantity is. But it is preciselythese small quantities of testing fluid that current and futureinjection nozzles must be able to reliably inject.

[0005] The object of the current invention, therefore, is to modify amethod of the type mentioned at the beginning so that it permits a moreprecise determination of the mass of the injected testing fluid and ofthe volume of testing fluid injected.

[0006] This object is attained in that the pressure of the testing fluidis detected in the measuring chamber and the measurement signal isprocessed taking into account the pressure detected.

ADVANTAGES OF THE INVENTION

[0007] This step results in the fact that with an injection of testingfluid, the actually injected fluid mass can be determined with greaterprecision. The invention was in fact based on the recognition that themass of a particular volume depends on the density prevailing in thisvolume. However, the density inside a volume also depends on thepressure prevailing in the volume.

[0008] Because the pressure, which prevails in the testing fluidcontained in the measuring chamber, is detected according to theinvention, the properties of the testing fluid in the measuring chambercan be precisely determined and consequently, the corresponding injectedmass can also be calculated precisely from the measured volume. Bytaking into account the pressure actually prevailing in the measuringchamber, it is also possible to convert the injected volume measured ata particular pressure into a particular comparison value (e.g. 1 bar).In this manner, it is very easily possible to compare differentinjections and different injection systems to one another since thesemeasured injection quantities are based on the same ambient conditions.

[0009] The method according to the invention thus makes thedetermination of the mass of testing fluid injected into the measuringchamber more precise and also permits the calculation of a volume basedon particular ambient conditions, which in turn permits a bettercomparison of different injection systems.

[0010] Advantageous modifications of the invention are disclosed in thedependent claims.

[0011] In a first modification, the invention proposes that thetemperature of the testing fluid be detected in the measuring chamberand that the measurement signal be processed taking into account thetemperature of the testing fluid. This modification assures that theproperties of the testing fluid contained in the measuring chamberdepend not only on the pressure but also on the temperature of thetesting fluid in the measuring chamber. This further increases theprecision and comparability of testing values.

[0012] Alternatively, the invention also proposes that taking intoaccount the measured pressure and possibly the measured temperature, thedensity of the testing fluid in the measuring chamber is determined andbased on this, a comparison volume at a particular comparison pressureand possibly at a particular comparison temperature is determined. Thisis a simple and very precise method for determining a parameter, whichcan be used to precisely compare the quality of different injectionsystems.

[0013] In another modification of the method according to the inventiondiscloses that the progression of the pressure during an injection isdetected and the measurement signal is processed taking into account thedetected progression of the pressure. This allows the method to takeinto account the fact that the pressure in the measuring chamber canchange during an injection.

[0014] The invention also proposes that when the pressure of the testingfluid in the measuring chamber exceeds a limit, an error message isgenerated. It is relatively important for the precision of themeasurement that the pressure of the testing fluid in the measuringchamber lie with a particular range of values. An excessive pressure inthe measuring chamber, like an insufficient pressure, can lead to adistortion of the measurement result. This fact is taken into account bythis modification.

[0015] It is particularly preferable that when the pressure of thetesting fluid in the measuring chamber exceeds a limit, a safety deviceis activated, which reduces the pressure of the testing fluid in themeasuring chamber. For example, it is possible that the movement of thepiston might become blocked. In this instance, the pressure in themeasuring chamber during an injection could reach a level that iscritical for the measuring device. This can be detected by the pressuremeasurement and appropriate countermeasures can be initiated.

[0016] The current invention also relates to a computer program, whichis suitable for executing the above method, when it is run on acomputer. It is particularly preferable if the computer program isstored in a memory, in particular a flash memory.

[0017] In addition, the invention relates to a device for measuring theinjection quantity of injection systems, in particular for motorvehicles, and in particular in production testing, having a measuringchamber into which a testing fluid can be injected by an injectionsystem, having a piston, which at least partially defines a measuringchamber, and having a detection device, which detects a movement of thepiston and generates a corresponding measurement signal.

[0018] In order to increase precision in the detection of the injectedfluid mass, and also to permit a better comparison of the injectionquantities and injection volumes measured in different injections, theinvention proposes that the device include a detection device for thepressure of the testing fluid in the measuring chamber as well as aprocessing unit in which the measurement signal is processed, takinginto account the pressure detected.

[0019] It is particularly preferable if the processing unit of thedevice is provided with a computer program according to one of thepreceding claims.

DRAWINGS

[0020] An exemplary embodiment of the invention will be explained indetail below in conjunction with the accompanying drawings.

[0021]FIG. 1 shows a section through an exemplary embodiment of a devicefor measuring the injection quantity of injection nozzles; and

[0022]FIG. 2 shows a flowchart of a method for operating the device fromFIG. 1.

DESCRIPTION OF THE EXEMPLARY EMBODIMENT

[0023] In FIG. 1, a device for measuring the injection quantity ofinjection systems is labeled as a whole with the reference numeral 10.It includes a centrally disposed body 12, which is secured to a sleeve14. This sleeve is in turn supported on a base plate 16. The device 10is fixed by means of the base plate 16.

[0024] An essentially central stepped bore 18 is let into the centralbody 12. A cylindrical insert 20 is inserted into the upper section ofthe stepped bore 18 and is supported by means of a collar 22 against thetop of the central body 12. A head 24 is placed onto the insert 20 in apressure-tight fashion, which likewise has a stepped bore 26 let intoit, which in the assembled state shown in FIG. 1, extends coaxial to thestepped bore 18. An adapter 28 is inserted from above into the steppedbore 26 and is sealed in relation to the stepped bore 26 by means ofO-rings 30. An injection system, in this instance an injector 32, isinserted with its injection nozzle 33 into the adapter 28. The injector32 is in turn connected to a high pressure testing fluid supply (notshown). An injection damper 34 is inserted into the lower region of thestepped bore 26 in the head 24.

[0025] The insert 20 also contains a bore 38, which in the installationposition shown in FIG. 1, extends coaxial to the stepped bore 18 and tothe stepped bore 26. A piston 40 is guided so that it can slide in thebore 38. A helical spring 42, which is supported against a transducerreceptacle 44, pushes the piston 40 upward. A measuring chamber 45 isdefined by the top end of the piston 40, the lower unthreaded region ofthe injection damper 34, and the lower region of the stepped bore 26.The piston 40 is embodied as a closed, hollow body.

[0026] The measuring chamber 45 formed between the piston 40 and thehead 24 is filled with a testing fluid (unnumbered). The pressure ofthis testing fluid in the measuring chamber 45 is measured by a pressuresensor 50, which is disposed outside the intersecting plane of FIG. 1and is therefore only depicted symbolically in the drawing. The pressuresensor 50 is inserted into the measuring chamber 45 through an obliquethrough bore (not shown). A temperature sensor 46 detects thetemperature of the testing fluid in the measuring chamber 45. Thepressure sensor 50 and the temperature sensor 46 are connected to acontrol and processing unit 52, whose output is connected to a magneticdrain valve 53, through which the testing fluid can be drained from themeasuring chamber 45. To the left of the central body 12, there is alsoa constant pressure valve 54, which, even at very different gaspressures underneath the piston 40, provides for a drainage rate fromthe measuring chamber 45 that is virtually independent of the gaspressure underneath the piston 40 when the electromagnetically actuateddrain valve 53 is open.

[0027] The transducer receptacle 44 likewise contains a stepped bore 56,which in the installation position shown in FIG. 1, is likewise coaxialto the other stepped bores 18, 26, and 38. A spring retainer 58 with acylindrical shoulder 60 is mounted onto the underside of the transducerreceptacle 44. The shoulder 60 engages in the stepped bore 56. Thespring retainer 58 and its shoulder 60 also have a central stepped bore62, which is open toward the bottom.

[0028] A shoulder of the stepped bore 62 in the spring retainer 58supports a helical spring 64, which pushes a sensor retainer 66 upwardagainst a collar of the transducer receptacle 44 that protrudes radiallyinward. The sensor retainer 66 is tubular or sleeve-shaped and its upperregion has an eddy current sensor 68 screwed into it so that the top endof this sensor is a short distance under the bottom end of the piston40. A connecting line 70 of the eddy current sensor 68 is routed outwardthrough the tubular sensor retainer 66 and the spring retainer 58 and isconnected to the control and processing unit 52.

[0029] In the event of a malfunction, for example due to an insufficientemptying of the measuring chamber 45 between two injections or twoinjection cycles, if the piston 40 moves too far downward, then it comesto rest with its bottom end in contact with the top end of the eddycurrent sensor 68. Because the sensor retainer 66 is supported by thehelical spring 64, the piston 40, together with the eddy current sensor68 and the sensor retainer 66, can move further downward—in thisinstance counter to the initial spring stress of the helical spring 64.A downward motion of the piston 40 is possible provided that the testingfluid can flow out of the measuring chamber 45 through a circumferentialgroove (unnumbered) in the stepped bore 38 of the insert 20. Thisprevents damage to the device 10 in the event of a malfunction.

[0030] The device 10, which is depicted in FIG. 1 and is for measuringthe injection quantity of an injection nozzle 28, operates according tothe following method (see FIG. 2):

[0031] Testing fluid (not shown) is supplied by means of the highpressure testing fluid supply to the injection system 32 and itsinjection nozzle 33 and, by means of the injection damper 34, isinjected into the measuring chamber 45 that is likewise filled withtesting fluid. The injection damper 34 prevents the injection jets fromdirectly striking the top end of the piston 40. A direct impact of theinjection jets against the piston 40 could set the piston intooscillations, which do not correspond to the actual course of theinjection. The injection of testing fluid into the measuring chamber 45increases the testing fluid volume in the measuring chamber 45. Theadditional volume traveling into the measuring chamber 45 moves thepiston 40 downward, counter to the force of the helical spring 42 andthe gas pressure underneath the piston 40. This changes the distancebetween the bottom end of the piston 40 and the eddy current sensor 68.

[0032] This change in the distance between the eddy current sensor 68and the bottom end of the piston 40 results in a change in the complexinput impedance on the input side of the winding of the eddy currentsensor 68. This change is metrologically evaluated in the control andprocessing unit 52 and is used to determine a distance sm (block 72 inFIG. 2) that the piston 40 has traveled.

[0033] Based on the measured distance sm—after the start of thecalculation in block 71, a volume Vm is determined in block 74. Thiscorresponds to the volume by which the measuring chamber 45 hasincreased due to the movement of the piston 40. This volume iscalculated from the measured distance sm and the cross sectional area ofthe piston 40, which is waiting in block 76 and has been called up froma memory 78.

[0034] In block 80, this volume Vm, which is also referred to as the“displacement volume”, is used to calculate the injected mass mi oftesting fluid. This is done by multiplying the displacement volume Vm bythe density r of the testing fluid. However, the density r of thetesting fluid in the measuring chamber 45 on the one hand, depends onthe temperature T (block 82) and on the other hand, depends on thepressure p (block 84), which prevail in the testing fluid in themeasuring chamber 45. These are detected by the pressure sensor 50 andthe temperature sensor 46 and, based on the detected values, in block80, first the density r prevailing in the testing fluid in the measuringchamber 45 is determined at the detected pressure p and the detectedtemperature T, and based on this density, the injected mass mi isdetermined.

[0035] Based on the actually injected mass mi of testing fluid, whichhas been injected into the measuring chamber 45, in block 86, acomparison or norm volume Vnorm is calculated based on a determinedpressure pnorm and a determined temperature tnorm (block 88). Thiscomparison or norm volume Vnorm is particularly well-suited forcomparing different injections and for comparing different injectionsystems 32. The method depicted in FIG. 2 ends at block 92.

[0036] The device shown in FIG. 1 and the method shown in FIG. 2 canconsiderably improve the precision in the calculation of a volumeinjected into the measuring chamber 45 under defined norm conditions(norm temperature and norm pressure) and in the calculation of theactually injected testing fluid mass. This increase in precision has anespecially significant effect, particularly on the measurement of smallinjection quantities.

[0037] In an exemplary embodiment that is not shown, the pressure, whichprevails in the testing fluid in the measuring chamber and is detectedby the pressure sensor, is also used for malfunction and safetymonitoring of the device. If the pressure of the testing fluid in themeasuring chamber lies beyond a defined limit, then it can be assumedthat there is a malfunction in the system so that an error message isgenerated. For example with a jammed piston, a very rapid increase inthe pressure in the measuring chamber can occur, which can cause damageto the device. In this instance, when the pressure of the testing fluidin the measuring chamber exceeds a limit, the magnetic drain valve istriggered by the control and processing unit so that the valve opens andtesting fluid is drained from the measuring chamber and the pressure inthe measuring chamber is reduced. This reliably prevents damage to thedevice for example due to a jamming of the piston.

1. A method for measuring the injection quantity of injection systems,in particular for motor vehicles and in particular in productiontesting, in which an injection system (32, 33) injects a testing fluidinto a measuring chamber (45) and the movement that an injectionproduces in a piston (40), which at least partially defines themeasuring chamber (45), is detected by a detection device (52), whichgenerates a measurement signal (sm), characterized in that the pressure(p) of the testing fluid in the measuring chamber (45) is detected andthe measurement signal (sm) is processed (80) taking into account thedetected pressure (p).
 2. The method according to claim 1, characterizedin that the temperature (T) of the testing fluid in the measuringchamber (45) is detected and the measurement signal (sm) is processed(80) taking into account the temperature (T) of the testing fluid. 3.The method according to one of claims 1 or 2, characterized in that,taking into account the detected pressure (p) and possibly the detectedtemperature (T), the density of the testing fluid in the measuringchamber (45) is determined and based on this, a comparison volume(Vnorm) is determined at a particular comparison pressure (pnorm) andpossibly at a particular comparison temperature (tnorm).
 4. The methodaccording to one of the preceding claims, characterized in that theprogression of the pressure during an injection is detected and themeasurement signal is processed taking into account the detectedprogression of the pressure.
 5. The method according to one of thepreceding claims, characterized in that when the pressure (p) of thetesting fluid in the measuring chamber (45) lies beyond a limit, anerror message is generated.
 6. The method according to claim 5,characterized in that when the pressure (p) of the testing fluid in themeasuring chamber (45) exceeds a limit, a safety device (53) isactivated, which reduces the pressure (p) of the testing fluid in themeasuring chamber (45).
 7. A computer program, characterized in that itis suitable for executing the method according to one of claims 1 to 6,when it is run on a computer.
 8. The computer program according to claim7, characterized in that it is stored in a memory, in particular a flashmemory.
 9. A device for measuring the injection quantity of injectionsystems (32, 33), in particular for motor vehicles and in particular inproduction testing, with a measuring chamber (45) into which aninjection system (32, 33) can inject a testing fluid, with a piston(40), which at least partially defines a measuring chamber (45), with adetection device (68), which detects a movement of the piston (40) andgenerates a corresponding measurement signal (sm), characterized in thatit includes a detecting device (50) for the pressure of the testingfluid in the measuring chamber (45) and a processing unit (52) in whichthe measurement signal (sm) is processed (80) taking into account thedetected pressure (p).
 10. The device according to claim 9,characterized in that the processing unit is provided with a computerprogram according to one of claims 7 or 8.